The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air and fuel mixture within cylinders to drive pistons. As air flow into the engine increases or decreases, a fuel control system adjusts an amount of fuel that is injected to provide a desired air/fuel mixture to the cylinders.
Referring now to FIG. 1, a functional block diagram of an engine system 100 is presented. The engine system 100 includes an engine 102 that combusts an air/fuel mixture. Air is drawn into an intake manifold 110 through a throttle valve 112. A control module 114 commands a throttle actuator module 116 to regulate opening of the throttle valve 112 to control the amount of air drawn into the intake manifold 110. The throttle actuator module 116 may monitor the position of the throttle valve 112 using one or more throttle position sensors (TPS) 117.
Air from the intake manifold 110 is drawn into cylinders of the engine 102. While the engine 102 may include multiple cylinders, for illustration purposes, a single representative cylinder 118 is shown. For example only, the engine 102 may include 2, 3, 4, 5, 6, 8, 10, and/or 12 cylinders.
Air from the intake manifold 110 is drawn into the cylinder 118 through an intake valve 122. The control module 114 controls the amount of fuel injected by a fuel injection system 124. The fuel injection system 124 may inject fuel into the intake manifold 110 at a central location or may inject fuel into the intake manifold 110 at multiple locations, such as near the intake valve of each of the cylinders. Alternatively, the fuel injection system 124 may inject fuel directly into the cylinders.
The injected fuel mixes with the air and creates the air/fuel mixture in the cylinder 118. A piston (not shown) within the cylinder 118 compresses the air/fuel mixture. Based on a signal from the control module 114, an ignition of the air/fuel mixture occurs. The timing of the ignition may be specified relative to a time when the piston is at a topmost position (referred to as top dead center (TDC)), a point at which compression of the air/fuel mixture is maximized.
The combustion of the air/fuel mixture drives the piston down (i.e. initiates a combustion stroke), thereby driving a rotating crankshaft (not shown). The piston expels byproducts of combustion through an exhaust valve 130 during a following exhaust stroke. The byproducts of combustion are exhausted from the vehicle via an exhaust system 134.
Engine coolant is used to cool the engine. A temperature of the engine coolant may be measured using an engine coolant temperature (ECT) sensor 182. The ECT sensor 182 may be located within the engine 102 or at other locations where the coolant is circulated, such as a radiator (not shown).
After the piston reaches TDC (i.e. after the exhaust stroke), the air/fuel mixture is injected into the cylinder 118 during an intake stroke. After a bottom dead center (BDC) position, the air/fuel mixture is compressed during a combustion stroke. When the piston reaches TDC, a spark ignites the compressed air/fuel mixture.
During the combustion process, the temperature of the piston increases significantly. Methods used to cool the piston may include enriching the air/fuel mixture and/or adding piston squirters. Piston squirters spray oil at a skirt of the piston.